Contact lenses are lenses widely used to correct vision and are designed to be placed directly on the surface of the eye so as to cover a substantial portion of the cornea. A contact lens having particular curvature(s) bends light in a substantially even manner and is commonly used to correct various conditions of the eye.
Some contact lenses are made as orthokeratologic lenses which are designed to reshape the cornea so as to reduce refractive errors that may arise in certain ophthalmologic conditions. FIG. 1A depicts a conventional orthokeratologic contact lens having a largely hemispherical shape, where the lens is subdivided into various regions which may or may not have differing curvature(s). A toric contact lens exhibits focusing powers that will vary depending on the direction of incident light and is often used to correct for astigmatism. Multifocal contact lenses (e.g., bifocal lenses) are designed to have multiple focal points and are typically used to correct for presbyopia, which arises from the eye exhibiting a diminished ability (e.g., due to age) to focus on objects situated relatively close to the eye (e.g., reading material).
Some contact lenses are made from a soft material, such as a hydrogel or a silicone hydrogel. Silicone hydrogels are high in oxygen permeability relative to regular hydrogels. Rigid gas permeable lenses may be made from waterless polymers (e.g., non-hydrogel polymers) that are more rigid and generally smaller in diameter than hydrogel lenses. Rigid gas permeable lenses typically provide sharper vision than lenses made from a hydrogel and are commonly used as lenses for orthokeratologic treatment.